Lubricants



Nov.

Filed June 20, 1960 2 Sheets-Sheet 1 :20- LL. K 3 Z 90- GREASE I m 1 D E 2 GREASE E g 60- v GREASE 0 g GREASE 0 I- O V 30- v Y\ I- E r o- MILLING TEMP. F

INVENTORS BILL MITACEK J.P. GRAHAM A T TORNEYS United States Patent 3,112,270 LUBRICANTS Bill Mitacelr and John P. Graham, Bartlesville, Okla.,

assignors to Phillips Petroleum Company, a corporation of Delaware Filed June 20, 1960, Ser. No. 37,332 21 Claims. (Cl. 252-41) This invention relates to improved lubricants and in particular to bodied lubricants such as greases and to their method of manufacture.

Up to the present time the most successful commercial greases for general purpose automotive lubrication have been prepared from lubricating oils with metal salts of fatty acids as the thickening agent. The lithium soap greases, those containing the lithium salt of lZ-hydroxystearic acid, have been especially outstanding in such properties as work stability. Various synthetic thickeners, e.g. certain polymeric materials, have been suggested as replacements for soaps in grease compositions but by and large such materials do not stand up under the rigorous conditions of machine lubrication. For example, polyethylene prepared by the process of Fawcett et a1., U.S. 2,153,533, has been tried as av grease component and although the resulting products were suitable for salves or medicinal purposes (US. 2,628,127) they have not proven to be satisfactory for lubricating machinery.

One of the objections to the use of high molecular weight or normally solid polyethylene in greases has been its low solubility in hydrocarbon oils. This difiiculty has been overcome, at least in part, through the use of more branched materials such as the copolymers of ethylene with higher olefins (U.S. 2,327,705). In general, however, ethylene polymers serve merely to form a gel with the lubricating oil, this gel quickly breaking down to a relatively fluid consistency when the composition is subjected to mechanical working.

We have discovered that improved lubricants can be prepared from lubricating oil and ethylene polymer if the ethylene polymer has a density of at least 0.940 gram per cubic centimeter at 25 C. Ethylene polymers are now available in densities ranging all the way from about 0.91 to 0.97 and higher. Why the more dense of these materials proves to be so definitely superior in greases is not understood and is quite surprising, particularly since these more dense polymers are less soluble in the oils whose properties they modify. Nevertheless, we have definitely established that for some unexplainable reason ethylene polymers having a density of 0.940 and above behave in greases in an entirely diiferent manner from ethylene polymers which have a density less than 0.940 gram per cubic centimeter.

. In one aspect of our invention the high density ethylene polymer is added to a soap-thickened grease to produce a product having surprisingly enhanced properties.

In another aspect lubricating oil is thickened exclusively with the high density ethylene polymer to produce a grease of great endurance. In other words, the soap component can be reduced from its normal level and even left out altogether by increasing the amount of high density ethylene polymer present to give a grease of the desired properties. In a preferred embodiment of our invention the grease is thickened exclusively with high density ethylene polymer and is free of organic acid salts.

We have also discovered that in the production of greases containing high density ethylene polymer there is a critical temperature range within which the grease should be milled. In the manufacture of such greases a polymer dispersion is formed in the base oil by heating with agitation and the polymer-oil dispersion, either alone or in admixture with a soap-oil dispersion, is milled ac- 3,112,270 Patented Nov. 26,. 1963 "ice cording to techniques well understood in the art of making conventional greases but at certain critical temperatures. According to our invention greases of high work stability are prepared by milling the grease during manufacture at a temperature within the range of about to 210 F., preferably about 180 to 200 F.

It is an object of our invention to provide an improved lubricant.

Another object of our invention is to provide a grease having excellent work stability and a method of making such a grease.

Another object is to provide a soap-thickened grease which is improved with a lubricity additive.

Still another object is to provide a grease which is thickened exclusively with a synthetic polymer.

Still another object of our invention is to provide a method of making an improved grease containing high density ethylene polymer.

Other objects, advantages and features of our invention will be apparent to those skilled in the art from the following discussion and the drawings in which FIGURE 1 is a graph correlating milling temperatures with work stability for greases thickened with ethylene polymers of various densities, and

FIGURE 2 is a graph showing the improvement for the greases of our invention over one of the best types of soap thickened greases commercially available.

As stated previously, the polymers used in greases according to our invention are ethylene polymers having adensity at 25 C. of at least 0.940 gram per cubic centimeter. The density of these polymers generally will not exceed 0.970 although more dense, e.g. up to 1.00, polymers are possible and can be used. In this discussion we refer to these ethylene polymers as high density polymers. The term low density is reserved for those ethylene polymers which have a density below 0.940. In determining the density for these polymers we prefer that the following procedure be followed.

In density determinations the specimens should be prepared by compression molding the polymer at 340 F. until completely molten followed by cooling to 200 F. at a rate of about 10 F. per minute. Water is then circulated through the mold jacket to continue the cooling to 150 F. at a rate not exceeding 20 F. per minute. The polymer is then removed from the mold and cooled to room temperature.

Density is determined by placing a smooth, void-free, pea-sized specimen cut from a compression molded slab of the polymer in a 50 mL, glass-stoppered graduate. Carbon tetrachloride and methylcyclohexane are added to the graduate from burettes in proportion such that the specimen is suspended in the solution. During the addition of the liquids the graduate is shaken to secure thorough mixing. When the mixture just suspends the specimen, a portion of the liquid is transferred to a small test tube and placed on the platform of a Westphal balance and the glass bob lowered therein. With the temperature shown by the thermometer in the bob in the range 73-78" F., the balance is adjusted until the pointer is at zero. The value shown in the scale is taken as the specific gravity. With the balance standardized to read 1.000 with a sample of distilled water at 4 C. the specific gravity will be numerically equal to density in grams per cc.

Of course, other procedures which produce equivalent results can be used.

The ethylene polymers which are employed in our invention include the homopolymer, polyethylene, as well as copolymers of ethylene with olefins of higher molecular weight, e.g. up to 8 carbon atoms per molecule, preferably containing no branching nearer the double bond than the 4-position. Examples of suitable comonomers include propylene, l-butene, Z-butene, l-pentene, l-octene, 4- methyl-l-pentene, 4-ethyl-l-pentene, 4-methyl-1-hexene, 6-methyl-l-heptene, 4-ethyl-1-hexene, and the like. We prefer the copolymers of ethylene with propylene or 1- butene. In general, ethylene makes up at least 95 Weight percent of the copolymer. In forming such a polymer the monomer feed to the polymerization zone will ordinarily be at least 80 percent by weight ethylene. As the percent of ethylene in the copolymer is decreased the density of the polymer likewise is decreased so that the density limitation can be used as an indication of copolymer composition. In other words, if the density of the copolymer is 0.940 or above, it will be suitable for our invention.

Methods of preparing the ethylene polymers of high density are now well known. A preferred method is described in the United States Patent 2,825,721, which issued March 4, 1958, to I. P. Hogan et al. Suitable polymers can be prepared in other low pressure processes, for example, processes which employ what are commercially known as organometal catalyst systems.

The greases of our invention contain a lubricating oil base, for example, mineral, vegetable, or animal oils or a mixture. We prefer that at least a major amount of the lubricating base oil be mineral in origin, preferably a refined oil having a viscosity of about 50 to 240 SUS at 210 F. With the same amount and melt index of polymer the less viscous oils will make lighter greases and harder greases can be prepared from the more viscous types, e.g., 70 to 240 SUS at 210 F. White mineral oil can be used to make non-staining greases which are highly suitable for lubricating machinery in the textile and food industries. We prefer parafiinic oils for the preparation of greases of low graininess. Bright stocks thickened exclusively with high density ethylene polymers find special utility in lubricating sealed ball joints and other sealed units in automobiles. These greases can provide satisfactory lubrication for the life of the sealed units.

Soap-thickened greases which are well known in the art can be improved with the incorporation of high density ethylene polymer as a lubricity additive. Commonly used soaps include the metal salts of high molecular weight acids, e.g., acids of 10 to 30, preferably 16 to 24 carbon atoms, either synthetic or of animal or vegetable origin. Generally the alkali metal (sodium, lithium, potassium) or alkaline earth metal (calcium, barium, strontium, magnesium) salts of such acids as capric, lauric, myristic, palmitic, stean'c, oleic, linoleic, arachidic, behenic, heptacosanoic, triacontanoic, and the like, acids, normally in admixture are used. Hydroxy-substituted acid derivatives of these can also be employed. Esters, such as the glycerides, of these acids are frequently used. The soap-thickened greases which we prefer are those containing the lithium soap of 12-hydroxy-stearic acid as described in US. 2,397,956 of H. M. Fraser.

The amount of soap in the greases can range up to 25 ercent by weight. Generally if soap is used it is present in an amount of at least about weight percent although smaller amounts, e.g. 0.1 to 5 percent, can be used with substantial amounts, e.g. 5 to percent, of high density ethylene polymer. Normally the soap concentration in the grease does not exceed 15 weight percent.

The amount of ethylene polymer in the grease depends upon the type of grease desired, hard or light, and the melt index of the polymer used. For example, the melt index of the high density ethylene polymers which we use can vary over a broad range, i.e. from about 0.1 to 25, although we prefer to work with those having a melt index of about 1 to 6. More polymer of a higher melt index can be incorporated into the grease with less stiffening effect. By varying both the melt index of the polymer and the polymer concentration, greases covering a wide range of consistencies are possible. Melt index is determined by ASTM DQ38 571? except that five cuts are made and an average of these is determined.

Broadly, the amount of ethylene polymer can vary in the range of about 0.1 to 20 weight percent of the finished grease depending upon the above considerations. In soapless greases the concentration of polymer is above about 1.0 percent and preferably at least 2 percent.

Two types of greases have proven to be especially outstanding in their physical properties and efiectiveness as a lubricant. These are (1) a soap grease containing about 0.1 to 4, preferably 0.5 to 2.5, weight percent high density ethylene polymer as a lubricity additive, and (2) a soapless grease containing about 4 to 12, preferably 5 to 10, weight percent high density ethylene polymer.

It should be understood that other materials normally used in greases can be added to the compositions of our invention. For example, various additives such as rust inhibitors antioxidants, and the like are frequently included. Other modifiers such as fillers, pigments, perfumes and the like can be used. Examples of such materials include propylenediamine, phenyl-alpha-naphthylamine, phenothiazine, mica, asbestos, powdered lead, powdered zinc, talc, alumina, zinc oxide, titanium dioxide, montmorillonite, attapulgite, molybdenum disulfide, organophilic montmorillonites (Bentones), calcium carbonate, basic lead carbonate, calcium silicate, graphite, nitrobenzene, carbon black and the like. Generally, the amount of these modifiers is less than about 10 percent of the total weight of the grease.

In preparing the greases of our invention the ethylene polymer is dispersed in the base lubricants by heating the oil with agitation. The solid polymer can be used either in pellet form or more finely divided. Heating the oil to about 325 to 450 F. and more frequently above 380 'F. is required to form a satisfactory polymer-oil dispersion. Generally the polymer is adequately dispersed within about 1 to 60 minutes.

If a soap grease is to be made, soap and polymer concentrates are normally prepared separately and then blended prior to milling. Preparation of the soap concentrate follows normal procedures, as discussed, for example, by Boner, Manufacture and Application of Lubricating Greases, chapter 5, Reinhold Publishing Corp, New York (1954). Generally from 0.33 to 4 volumes of soap concentrate are mixed with 1 volume of polymer concentrate. We prefer to blend these concentrates at about 270 to 320 F., or above the cloud point of the ethylene polymer.

The work stability of our greases with respect to milling temperature is quite unexpected. Unlike greases of the prior art which are preferably milled at relatively low temperatures, e.g. below F., for maximum work stability, the greases of our invention exhibit a maximum stability when milled between about and 210 F., preferably between 180 and 200 F. By milling we refer to a processing step that is well understood in grease manufacture. Basically, it is severe agitation which produces substantial shearing in the mixture. Preferably the grease milling is carried out in colloid mills which are operated at high speeds with relatively close clearances, for instance on the order of 3000 to 9000 rpm. and 0.001 to 0.003 inch clearance. A number of suitable grease mills are commercially available. In some the grease is passed between closely spaced counter-rotating disks. A preferred type employs tapered, grooved rotors and stators with adjustable clearance. Mills or homogenizers which produce shearing forces on the grease by passing the grease through one or more orifices under high pressure can also be used. A good discussion of grease milling has been made by Boner (supra).

The greases can be cooled to milling temperature at any rate with or without agitation or cooled to below milling temperature and reheated either prior to or during milling. Normally, there is some increase in grease temperature within the mill as a result of the mechanical working. 'In general, vigorous agitation or quick cooling with less vigorous agitation during the cooling step prior to milling produces a fibrous grease while smooth, buttery greases result from slow cooling Without agitation.

Advantages of this invention are illustrated by the following examples. The reactants, and their proportions, and other specific conditions are presented as being typical and should not be construed to limit the invention unduly.

EXAMPLE I Three types of lithium soap grease were prepared: one containing 1 weight percent high density polyethylene (grease A), one containing 1 weight percent low density polyethylene (grease B), and one containing no polyethylene (grease C). in each case a soap concentrate was first prepared, formulated as follows:

The vessel was closed and the reactants heated to 350 F. over about a 45 minute interval. During this time the pressure increased to about 100 p.s.i.g. The pressure was then decreased to atmospheric pressure. The mixture was cooled to about 280 F.

Polyethylene concentrates of 2 weight percent were prepared by mixing the polyethylenes with naphthenic oil (75 to 95 SUS at 210 F.) While heating. The high density polyethylene had a density of 0.96 gram per cubic centimeter, a melt index of 5, and a softening point of 260 F. Solution of this polyethylene was effected by heating the oil mixture to 400 F. The low density polyethylene had a density of 0.92 gram per cubic centimeter, a melt index of 20, and a softening point of 183 F. The solution of low density polyethylene was effected by heating the mixture to 325 F.

The polyethylene concentrates and the soap concentrates were cooled to about 280 F. and blended with more naphthenic oil as follows:

Weight Percent Grease A Grease B Grease O Soap concentrate 42. 5 42. 5 42. 5 High density polyethylene eoneentrate 50. Low density polyethylene concentrate" 50. 0 Oil 7. 7. 5 57. 5 100.0 100.0 100.0

Table 1 Cone Penetrations d Ooefil- Endur- Grease Relative cient of mice,

Torque Friction Minutes Unworked 60XX XX it Average of four valuesall 00+.

b Average of three values ranging between 2.5 and 4.8 minutes. Average of [our values ranging between 0.5 and 2.0 minutes. d XX=strokcs.

The cone penetration data indicate that all greases may be considered of the same type with regard to hardness and would be classed as NLGI Grade 2 products. All the products are considered satisfactory for use as wheel bearing lubricants, i.e. the leakage is less than 15 grains. The grease prepared with the high density polyethylene has greater lubricity as shown by the values for relative torque and the values for the coefficient of friction. The values for the endurance show that the use of the high density polymer gave a grease having an endurance value 17 times greater than the grease prepared with the low density product.

The procedures employed for the grease tests were as follows:

Cone penetrati0n.ASTM Method D217-52T.

Wheel bearing.ASTM -Dl26353T, except that the temperature employed was 260 F. rather than 220 F. and the grease loading was grams rather than 90 grams. This applies conditions severe than the unmodi fied test.

Coefiicz'ent of friction-The coefiicient of friction between a rotating steel ring and a steel test block when lubricated with the candidate greases was determined using a Timken E.P. tester manufactured by the Timken Roller Bearing Company, Canton, Ohio. Details of the apparatus and its operation have been described as Proposed Method of Test for Measurement of Extreme Pressure Properties of Lubricants, ASTM Bulletin, No. 228, pages 28-32, February 8. In this test 'a steel ring is rotated against a steel test block while the grease is fed to the point of contact of the test members. The grease at room temperature (70 to 80 F.) is fed at a constant rate by means of a pump. The mandrel speed is set at 800 r.p.m. and a ten-pound load is applied to the lever arm. The coefiicient of friction is then computed from the equation:

9.45(B+R) 10(A+C)2.5(B+R) where B=friction lever weight, lbs. R=sliding Weight reading, lbs. A=load lever weight, lbs. C'-=load weight constant, lbs.

Steering t0rque.--Knapp and Panger, NLGI Spokesman, volume 22, No. 7, pages 331-334, October 1958.

Endurance test.The Timken E.P. tester described above was used to ascertain the endurance of the candidate greases. The endurance is a measure of the time the grease will prevent seizure under the prescribed conditions. The test is reported in detail in the NLGI Spokesman, volume XX, No. 9, page 36, December 1956.

Grease A was found to be non-abrasive (ASTM D1404-5 6T) and to have a dropping point (ASTM D566 42), dispensability (ASTM D109255) and oxidation stability (ASTM D94250) substantially the same as grease C, which is a commercial grease of high quality. Grease A was superior to grease C in the high speed ball bearing tests (McKee tester) and also exhibited superior penetration stability over 0 to 77 F. Grease A was excellent in the water washout test (ASTM D1264-53T) and superior to greases B and C in bleeding (Federal Spec. 322T) as shown in Table II.

Table 11 Percent oil bled (0.25 p.s.i.g.,

EXAMPLE II Seven different greases were prepared using ethylene polymers of various densities as the sole thickening agent. Formulations were as follows:

Table IIIContinued [Grease F (Polymer Density=0.959)] Component: Weight percent 011 1 91'952 Cone Penetration at Ethylene polymer 8.00 Mill Out- 77 F: Change in Antioxidant 3 0.008 Run fl o 333 215 RIlSt inhibitor 4 0.04 Unworked GOXX I 1 A commercial, solvent refined oil of a highly paraflinic type having the following properties: SUS viscosity at 100 and 210 F. of 4130 and 209.3, respectively; viscosity index of 97; neutralization number 01' 0.00; 166 5 445 Conradson carbon of 0.0%; API gravity at 60 F. of 25.0; flash point of 178 L6 439 13 615 F.; and a pour point of plus 15 F. 196 398 439 3 3 The properties of the various ethylene polymers were as follows: 200 377 434 Ethylene Polymer I 15 [Grease G (Polymer Dcusity=0.949)] Density fig f i Index 23 150 222 26c 44 150 211 26G 55 153 2g; 27% 40 Grease D 0. 063 5. 79 16 9 Grease E 0.903 1.5 g 3 Z4 9 Grease 0. 95s 20. 2 $0 Grease G... 0. 9 19 0.6 M Z Zfifi 51 Grease H- 0. 033 3. 80 230 49 Grease 1.- 0.917 1. 86 Grease J 0. 010 12. G8

[Grease H (Polymer Density=0.933)] 3 Sautowhite Crystals, Monsanto Chemical Company, identified as: 4,4-thiobis(S-tert'hutyl-m-crcsol).

4 A commercial product, Parabar 448, from the Enjoy Company. 084 15 To prepare the greases the following process was em- 2% ployed. The oil was heated to a temperature of about 190 366 4 at 350 F. The polymer was added to the hot 011 with stirring and While continuing heating of the oil to a tem- 515 162 531 10s perature of about 400 P. so as to dissolve the polymer. 215 The operation of dispersing the polymer with heating required about 30-40 minutes. Each mixture was then cooled over a period of about 3 to 4 hours to a tempera- 35 [Grease I (Polymer Densltyflgln ture within the range of 65 to 100 F., except as noted for two runs in the tabulation of results, Table III. Each 128 300 420 so grease composition was then milled in a Charlotte col- 134 2' 2 139 set 459 .15 lord mill, Model ND-l, equipped with a Type P head 149 300 43g -15 and having a mill clearance of 0.001 inch. The tempera- 23g ture of milling was controlled by control of the rate of 161 430 4 53 23 circulation of cooling water to the mill head. In this manner the milling temperature was varied as shown in 176 196 279 83 Table III for the various greases prepared with each fig 5': candidate polymer. The milled greases were deaerated 195 226 305 79 by extrusion from the mill into an evacuated vessel. The

pressure in the vessel was below about 20 mm. of mercury.

The work stability of the products was determined by the Cone Penetration Test Procedure described by ASTM Method D217-52T. The results of these tests are summarized in Table III and in FIGURE 1.

Table III [Grease D (Polymer Density=0.963)} Mill input temperatures were -100 I". for all runs except for these runs. For these runs the input temperatures were 122 and 169 11, respectively.

The above data which is shown graphically in FIG- URE 1 illustrate two important and completely unexpected distinctions of the greases containing high density ethylene polymer over the greases thickened with the low density polymer. First, it is possible to prepare a soapless grease with the high density polymer having a work stability which compares favorably with the best soap greases currently available. Also, the high density polymer-thickened greases exhibit a characteristic curve on the stability-milling temperature plot (FIGURE 1) which indicates an optimum milling temperature between about 170 to 210 F.

Greases D and G follow substantially the same curve, while the results with greases E and F indicate that somewhat higher milling temperatures can be used with the polymers of lower melt index and vice versa. Grease H made with 0.933 density polymer behaved in an entirely difierent manner in evidence that higher milling temperatures definitely are not to he favored. Grease I gave results that were erratic and appeared to follow no well 1 Procedure described in NLGI Spokesman, volume XX, No. 9, page 36. December 1956, and run with a 14-p0undload.

I ASTM Dl263-53T using 90 g. charge and 220 F.

3 ASTM D566-42.

4 Roll mill.

The surprisingly superior endurance lives of greases G and D are shown in the above data. For these greases the test was arbitrarily terminated after 10 hours. The greases containing high density polymer were also superior in the wheel bearing leakage tests. A pass value is designated for greases having a leakage value of 15 grams or less.

EXAMPLE III Two soapless greases were prepared from oil and ethylene polymer the same as that used for grease D (0.963 density) of Example II, with the polymer at different concentration levels. The greases were made by heating the oil to 350 F. and adding the polyethylene gradually over a 5-minute period while continuing to heat the mixture to 400 'F. The polymer was dispersed with stirring in about 30 to 40 minutes. Each mixture was cooled for 3 to 4 hours without agitation to a temperature below its milling temperature. The greases were milled in a Charlotte colloid mill. Cone penetration values on these greases were determined according to ASTM D2l7-52T. These data are reported in Table V.

Table V Cone Penetration Batch Milling Polymer, Temperature, percent F. Unworked GOXX XX A (OP) The results again show that the most stable greases were prepared by milling at a temperature between 170 and 210 F. with milling temperatures of about 180 to 195 F. preferred. The A CP values given represent the difference between the unworked and the eoxx penetration values. It is interesting to note that the above A CP data falls on substantially the same curve shown in FIGURE 1 for 8 percent polymer concentration. Thus it appears that critical milling temperature depends not so much on polymer concentration in the grease as on polymer density.

EXAMPLE IV Several other greases were prepared as formulated and described in Example III using a polymer having a density of 0.963 except that these greases were cooled and milled on a roll mill at room temperature to examine a correlation between polymer concentration and unworked penetration value. These results are shown in Table VI.

Table VI Unworked Polymer concentration penetration weight percent: value 1 500 2 400 4.8 300 7.4 250 10.6 200 As might be expected, stiffer greases are produced with increasing amounts of polymer. We discovered, however, that compared to the above grease containing high density polymer from 2 to 3 times as much low density polyethylene (0.910 g./cc.) was required to produce greases of equivalent unworked consistency.

EXAMPLE V Two types of grease were prepared as follows:

Grease K: Same formulation and procedure as for grease C, Example I (contains soap but no polyethylene). Grease L: Same as grease in Example IV with 6 weight percent polyethylene (polyethylene density 0.963, contains no soap).

These products and grease A of Example I (polymer density 0.96, contains soap) were evaluated for coefiicient of friction using the procedure of Example I with varying loads applied to the lever arm of the test apparatus. The results are shown in FIGURE 2. In all cases the load was increased during the test. Grease L was further tested by decreasing the load (broken line). A comparison of the curves for greases A and K shows a marked reduction in friction for the grease containing polyethylene as well as a decrease in the slope of the curve. In the soapless grease (grease L) the coefficient of friction value decreased with an increase in load (negative slope), and the grease apparently had a beneficial conditioning eifect on the steel surfaces of the last equipment as indicated by the lower values for coefficient of friction as the load was decreased.

EXAMPLE VI A soap grease formulated as grease A was prepared except that after the soap and polyethylene components were mixed the milling step was omitted. This product was tested for leakage tendencies in wheel bearings as described in Example I. The result was 46.0 grams leakage, which is unsatisfactory for use in automotive wheel bearings.

EXAMPLE VII A soap grease (grease M) was formulated as described for grease A and milled at F. Two other greases (N and 0) were prepared in the same manner except that the concentrates were mixed in the following proporions:

Weight (percent) Soap concentrate 47.5 Polymer concentrate 50.0 Oil 2.5

Grease N was milled at F. and grease O was milled at 280 F.

Three other greases (P, Q and R) were prepared with substantially the same formulation and procedure as for grease A except that the soap and polymer concentrates were mixed 50-50. Grease P was not milled, grease Q was milled at room temperature, and grease R was milled at 240 F. Cone penetration values are shown below:

The above data indicate that milling temperatures of about 170 to 200 F. provide the most stable soap greases in which ethylene polymer has been incorporated as a lubricity additive.

EXAMPLE VIII A grease similar to grease D of Example II was prepared containing 8 weight percent of 0.963 density polyethylene but no antioxidant or rust inhibitor. The polymer was dispersed at about 400 F. and the grease milled at approximately 180 F. This grease was quite work stable, having an unworked cone penetration at 77 F. of 295, 310 at 60 strokes, and 320 at 10,000 strokes. The Timken endurance life of the grease under 14-pound load was in excess of 600 minutes.

EXAMPLE IX In a semi-continuous run grease formulated as grease D of Example II was prepared. After forming a dispersion at 400 F. in an open kettle, the mixture was pumped through a Votator (a 3 x 12" indirect heat exchanger tube fitted with a scraper) where the grease was cooled from 375 F. to 95 F. The cooled dispersion was passed continuously from the Votator through a Charlotte colloid mill set for a clearance of 0.001 inch. The temperature of the grease leaving the mill was 200 F. The grease was then deaerated by stirring in a vessel under vacuum. This grease had an unworked cone penetration at 77 F. of 298, 305 at 60 strokes, and 308 at 10,000 strokes.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope thereof.

We claim:

1. A lubricant comprising a major amount of lubricating oil and from 0.1 to 20 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

2. An improved bodied lubricant comprising a major amount of mineral oil and from 0.1 to 20 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

3. An improved soap-thickened grease containing about 71 to 94.9 weight percent mineral oil, from to 15 weight percent soap, and as a lubricity additive from 0.1 to 4 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

4. A soapless lubricant comprising about 70 to 99 weight percent mineral oil and 1.0 to weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at C.

5. A soapless grease comprising about 78 to 96 weight percent mineral oil and about 4 to 12 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

6. An improved soapless grease which has been milled 12 at a temperature of about 170 to 210 F. and which contains about 78 to 98 weight percent mineral oil and as the thickening agent from. 2 to 12 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

7. The grease of claim 6 wherein said ethylene polymer is polyethylene.

8. An improved soapless grease comprising about to weight percent mineral lubricating oil and about 5 to 10 weight percent ethylene polymer having a density of at least 0.940, said grease having been milled at a temperature in the range of to 210 F.

9. The grease of claim 8 wherein said oil is white mineral oil.

10. The grease of claim 8 wherein said oil is a refined mineral oil having a viscosity of about 50 to 240 SUS at 210 F.

11. An improved soap-thickened grease comprising about 61 to 94.9 weight percent mineral lubricating oil, about 5 to 25 weight percent based upon the total composition of soap and about 0.1 to 4 weight percent of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

12. The grease of claim 11 wherein said soap contains the lithium salt of 12-hydroxy stearic acid.

13. A method of making a bodied lubricant which comprises dispersing from 0.1 to 20 weight percent based on the total composition of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C. in a major amount of lubricating oil at an elevated temperature above the cloud point of said polymer to form a polymer-oil mixture, cooling said mixture and milling said mixture at a temperature in the range of 170 to 210 F.

14. A method of making a bodied lubricant which comprises dispersing an ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C. in mineral lubricating oil at a temperature above the cloud point of said polymer to form a polymer-oil dispersion containing from 1 to 12 weight percent polymer, cooling the resulting polymer-oil dispersion and milling said dispersion at a temperature in the range of 170 to 210 F.

15. A method of making a bodied lubricant which comprises dispersing 5 to 10 weight percent of an ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C. in refined mineral lubricating oil of paraflinic type at a temperature in the range of 325 to 450 F. with agitation, cooling the resulting mixture, and milling said mixture at about 180 to 200 F. to form a stable grease.

16. The method of claim 15 wherein said mixture is cooled to below 180 F. and reheated during milling.

17. An improved soap-thickened grease comprising about 75 to 94.9 weight percent mineral lubricating oil, about 0.1 to 5 weight percent based on the total composition of soap and about 5 to 10 weight percent of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

18. An improved soap-thickened grease comprising about 65 to 90 weight percent mineral lubricating oil, about 5 to 15 weight percent based on the total composition of soap and about 5 to 10 weight percent of ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C.

19. A method of making a bodied lubricant which comprises forming a mixture of ethylene polymer, soap and mineral oil, said ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C., dispersing said polymer in said mineral oil by heating above the cloud point of said polymer, and milling the resulting mixture at a temperature in the range of 170 to 210 F.

20. A method of making a bodied lubricant which comprises forming a mixture containing 5 to 15 weight percent soap and 0.5 to 2.5 Weight percent ethylene polymer having a density above 0.940 gram per cubic centimeter at 25 C. in refined paraffinic mineral oil having a viscosity of 70 to 240 SUS at 210 F., dispersing said polymer in the oil by heating to about 325 to 450 F, and milling said mixture at a temperature in the range of 170 to 210 F.

21. An improved soap-thickened grease comprising about 61 to 94.9 weight percent mineral lubricating oil, about 5 to 25 weight percent based upon the total composition of soap and about 0.1 to 4 Weight percent of 14 ethylene polymer having a density of at least 0.940 gram per cubic centimeter at 25 C., said grease having been milled at a temperature in the range of 170 to 210 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,833,718 Morway et a1 May 6, 1958 FOREIGN PATENTS 710,109 Great Britain June 9, 1954 767,002 Great Britain Ian. 30, 1957 

3. AN IMPROVED SOAP-THICKENED GREASE CONTAINING ABOUT 71 TO 94.9 WEIGHT PERCENT MINERAL OIL, FROM 5 TO 15 WEIGHT PERCENT SOAP, AND AS A LUBRICITY ADDITIVE FROM 0.1 TO 4 WEIGHT PERCENT BASED ON THE TOTAL COMPOSITION OF ETHYLENE POLYMER HAVING A DENSITY OF AT LEAST 0.940 GRAM PER CUBIC CENTIMETER AT 25* C. 